1. Field of the Invention
The present invention relates to a lamp unit of a vehicle headlamp, and particularly, relates to a projector-type lamp unit that uses a light-emitting element as a light source.
2. Related Art
In recent years, even in vehicle headlamps, lamp units that use a light-emitting element, such as a light-emitting diode, as a light source have been adopted.
For example, Patent Document 1 discloses a so-called projector-type lamp unit including a projection lens arranged on an optical axis extending in the longitudinal direction of a vehicle, a light-emitting element arranged so as to face upward behind a rear focal point of the projection lens and in the vicinity of the optical axis, and a reflector arranged so as to cover the light-emitting element from above and to reflect the light from the light-emitting element forward toward the optical axis.
In such a case, in the lamp unit disclosed in Patent Document 1, a mirror member that has an upward reflecting surface that upward reflects a portion of the reflected light from the reflector, and has a front end edge formed so as to pass through the rear focal point of the projection lens is provided between the reflector and the projection lens. A portion of the reflected light from the reflector is reflected upward by the mirror member, thereby forming a light distribution pattern for low beams that has a cut-off line as an inverted projection image of a front end edge of the upward reflecting surface at its upper end.
[Patent Document 1] JP-A-2005-166590
In the projector-type lamp unit provided with a mirror member as disclosed in the above Patent Document 1, a light distribution pattern for low beams that has clear cut-off lines at its upper end can be formed while the utilization efficiency of the light from the light-emitting element can be enhanced.
However, this lamp unit is configured such that a portion of the reflected light from a rear reflector is reflected upward by the mirror member. Thus, not only a region in the vicinity below the self-lane cut-off line in the light distribution pattern for low beams becomes bright, but also, a region in the vicinity below the opposite-lane cut-off line becomes bright. The light that forms the region in the vicinity below the opposite-lane cut-off line may be regularly reflected by a road surface that gets wet, for instance, during a rainy day and enter driver's eyes on the opposite lane. The light may enter driver's eyes on the opposite lane even a vehicle is pitched. Thus, there is a problem in that, if the light is excessively strong, large glare may be given to a driver in the opposite lane.